To date, transistors used in power electronic applications have typically been fabricated with silicon (Si) semiconductor materials. Common transistor devices for power applications include Si CoolMOS®, Si Power MOSFETs, and Si Insulated Gate Bipolar Transistors (IGBTs). More recently, silicon carbide (SiC) power devices have been considered. Group III nitride-based semiconductor devices, such as gallium nitride (GaN) devices, are now emerging as attractive candidates to carry large current densities, support high breakdown voltages and to provide very low on-resistance, ultra-fast switching times and improved power efficiency.
In some lateral transistor devices, such as a gallium nitride-based High Electron Mobility Transistor (HEMT), the source is coupled to the rear side of the substrate on which the transistor structure is formed. The source may be coupled by a conductive through substrate via (TSV) to the rear surface of the substrate.
Further improvements to the connection between the source and the rear surface of the substrate are desirable.